1 /*
   2  * Copyright (c) 2014, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_JFR_UTILITIES_JFRTRYLOCK_HPP
  26 #define SHARE_JFR_UTILITIES_JFRTRYLOCK_HPP
  27 
  28 #include "runtime/atomic.hpp"
  29 #include "runtime/orderAccess.hpp"
  30 #include "runtime/mutexLocker.hpp"
  31 #include "utilities/debug.hpp"
  32 
  33 class JfrTryLock {
  34  private:
  35   volatile int* const _lock;
  36   bool _has_lock;
  37 
  38  public:
  39   JfrTryLock(volatile int* lock) : _lock(lock), _has_lock(Atomic::cmpxchg(lock, 0, 1) == 0) {}
  40 
  41   ~JfrTryLock() {
  42     if (_has_lock) {
  43       OrderAccess::fence();
  44       *_lock = 0;
  45     }
  46   }
  47 
  48   bool has_lock() const {
  49     return _has_lock;
  50   }
  51 };
  52 
  53 class JfrMonitorTryLock : public StackObj {
  54  private:
  55   Monitor* _lock;
  56   bool _acquired;
  57 
  58  public:
  59   JfrMonitorTryLock(Monitor* lock) : _lock(lock), _acquired(lock->try_lock()) {}
  60 
  61   ~JfrMonitorTryLock() {
  62     if (_acquired) {
  63       assert(_lock->owned_by_self(), "invariant");
  64       _lock->unlock();
  65     }
  66   }
  67 
  68   bool acquired() const {
  69     return _acquired;
  70   }
  71 
  72 };
  73 
  74 #endif // SHARE_JFR_UTILITIES_JFRTRYLOCK_HPP